Let Lemmata 6.1 and 6.2 be proved.
Then, the proof of (i) \(\longrightarrow \)  (ii) of Proposition 6.1 can be done
similarly to [1]}. The proof of (ii) \(\longrightarrow \)  (i) of the proposition
can be derived from Lemmata 6.1 and 6.2, and we omit the details.
The proofs of the lemmata are provided in Appendix.
